Artificial or plastic slate for blackboards



IUD-U6) UHUDO Hill EREltLdZ [AHWI l H E.

ALFRED F. PARSHALL, OF KANSAS CITY, MISSOURI.

ARTIFICIAL OR PLASTIC SLATE FOR BLACKBOARDS.

SPECIFICATION forming part: of Letters Patent. No. 323,722, dated August 4,1885.

Application filed June 16, 1855.

principally in themannthctu re of black-boards 10 for schools, school-slates, &c.

The compound aml theprocess of making it and using it may be fully described in the following language:

The compound is composed of the following 1 substances, in about the proportions stated,

but the process of eompoundiugthem may be (No specimens.) 7

In order to vary the results to be attained in certain cases, I may add to the compound iabove descrlbed a munber of other ingredients, wlnch shall be governed by my jutgvaried without departing from t he in\'ention i as, for instance. in shading the eompouml with ditl'erent coloring substances. For the body 20 of the compound J employ that which I am about to describe, as I have found that; in practice it produces \crysatistiletory results. I first take about thirty (Jltl) parts of finely pulverized nuuice-stone, thirty ('30) parts 2 chromc- 'rembportion of any desired mineral eolorirmunatter that will harmonizmingredients, and fifteen parts ma 'nesia. 'lhe above-mentioued substances I mix together thoroughly with boiled linseed-oil to the consistency of a thin paste, and grind them thus mixed in a suitable mill, after which twenty-five (23) parts Portland cement are thoroughly mixed with t'tmnis then ready to be used. I prefer to apply the compound with a common hand-trowel; but any other appropriate instrument can be used for this purpose. the compouml dries it becomes hardened sufficiently for use, aml it may then he considered 0 as'complet'e.

I employ magnesia as an ingredient of my compound, because I have found that it.- produces a very desirable elasticity ot'.surt'ace.

ment in each case. For instance, to give a particular result, marble-dust or emery will be used in additiohmzpulverized slate.

The same remarks will apply to the .5131- ing-matters used in the compound, for I have found that the action of the matter known as -dro i-blaek upon the compound is difl'erent lrom theaction of ivory-black. So, also, may it be said of nltramarine-blue, mineral brown, and cln'ome-Yellow. In certain instances '1 may substitute any one or a number of these for the chrome-green before mentioned, as circumstances may point. out.

In connection with theboiled linseed oil. and in order to hasten the dryingprocess, in some instances it will be desirable to add a certain quantity of s iirits of tar ientine. Again, in some particu ar cases, a portion of the previously-specified Portland content may be displaced by a like portion of duster-0f iaris, and a better result will be an tan It on y the cement had been used; and in connection with magnesia I may sometimes add a quantity ot' talc or t'alcose earth as desired.

I claim The hereindescribed compound, consisting of pulverized pumice-stone, ehromegreen or other mineral coloringanatter, boiled linseedoil, and Portland cement, in substantially the proportions specified.

In testimony whereofI atiix my signature in presence of two witnesses.

ALFRED 1'. PA ltSl I A LL.

\Vitnesscs:

ll. 0. Romcn'rsox, I A. lu-zssos. 

